The studies outlined in this proposal aim to elucidate the structure of bacterial D-amino acid transaminase. The primary sequence will be determined and, in a cooperative project, the three-dimensional structure will be studied. In addition, the role of amino acid side chains in the catalytic reaction will be evaluated by specific chemical modifications of the enzyme. Spectral studies with substrate analogs will be undertaken in the hope of detecting some intermediates in the catalytic pathway. The mechanisms of inactivation of of this enzyme by Beta-haloamino acids will be further investigated and the site of reaction with the transaminase will be ascertained. We plan to determine how important this enzyme is with respect to bacterial growth. We will establish whether the inhibition of growth by Beta-haloamino acids is correlated with the loss in activity of this enzyme. Finally, studies with penicillin-resistant microorganisms will be performed.